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▼ [19a-D104-3] Voltage-controlled magnetic anisotropy of Fe/Co/Pd/MgO epitaxial multilayer
Keywords:Voltage-controlled magnetic anisotropy, Pd
Voltage-controlled magnetic anisotropy (VCMA) magnitude need to be increased for practical use. By inserting a heavy-metal layer such as Pt, at Fe/MgO interface, significant enhancement had been obtained [1]. Previously, we had reported the VCMA of Fe/Pd/MgO system. Although a declining observed due to Pd insertion, post-annealing treatment increased the VCMA which may be attributed to alloying of Fe and Pd [2]. In this present study, we inserted 3d-material (Co) and 4d-material (Pd) at Fe/MgO interface because high VCMA was reported in Co/Pd/MgO system [3]. Moreover, post-annealing treatment has been done to form alloying interface.
Multilayer film structure was grown onto MgO(001) substrate as depicted in Fig. Insertion layer thickness of Co (tCo) and Pd (tPd) were varied to 0–0.52 nm and 0–0.38 nm, respectively, on the same wafer. By this configuration, we can investigate several interfaces conditions: Fe/MgO, Fe/Co/MgO, Fe/Pd/MgO and Fe/Co/Pd/MgO. The characterization of VCMA effect was performed through spin-wave spectroscopy, by measuring frequency shift without and with voltage applications. Figure 2 shows the VCMA value as a function of Pd-thickness (tPd). Black square indicating Fe/Pd/MgO. It can be seen that by inserting Pd, VCMA increase slightly before declining as Pd-thickness increase. This trend reproduced our previous result [2]. Interestingly when the Co layer inserted, higher VCMA value was obtained. The configuration of tCo = 0.52 nm (~4 ML) and tPd = 0.19 nm (~1 ML) gave the highest VCMA about 180 fJ/Vm. In the presentation, the influence of post-annealing treatment will be discussed. This work was partially supported by ImPACT program and JSPS KAKENHI (No. 26103002).
Multilayer film structure was grown onto MgO(001) substrate as depicted in Fig. Insertion layer thickness of Co (tCo) and Pd (tPd) were varied to 0–0.52 nm and 0–0.38 nm, respectively, on the same wafer. By this configuration, we can investigate several interfaces conditions: Fe/MgO, Fe/Co/MgO, Fe/Pd/MgO and Fe/Co/Pd/MgO. The characterization of VCMA effect was performed through spin-wave spectroscopy, by measuring frequency shift without and with voltage applications. Figure 2 shows the VCMA value as a function of Pd-thickness (tPd). Black square indicating Fe/Pd/MgO. It can be seen that by inserting Pd, VCMA increase slightly before declining as Pd-thickness increase. This trend reproduced our previous result [2]. Interestingly when the Co layer inserted, higher VCMA value was obtained. The configuration of tCo = 0.52 nm (~4 ML) and tPd = 0.19 nm (~1 ML) gave the highest VCMA about 180 fJ/Vm. In the presentation, the influence of post-annealing treatment will be discussed. This work was partially supported by ImPACT program and JSPS KAKENHI (No. 26103002).